# Stretching the Field of View

### by James Su, Vision Science

#### Teaching Effectiveness Award Essay, 2007

As a graduate student instructor for VS 203B, Dioptrics and Physical Optics, I have the pleasure of working with all of the sixty first-year optometry students, who view this course only as a mathematical prerequisite to passing their first year. In reality, this is a course where they can learn something applicable and useful for their future clinical rotations and real-life practice. As it turns out, they only study to memorize such jargon as “Keplerian,” “exit pupil,” “vignetting,” “Ramsden circle,” “field of view,” etc., the equations related to those terms, and sample problem sets. Who can blame them? They don’t see the connection between understanding the actual optics at work and their clinical practice. If they are learning to improve the visual experience of patients, the least they should understand is the underlying mechanism of how physical optics works, and that is best done by understanding the simple pieces of optics equipment.

Setting out to debunk their present notion of passing the class solely by memorizing equations and sample problems, I started bringing different pieces of optics equipment that would set the topic for the day’s discussion section. My favorite remains the Keplerian telescope discussion. At a glance, it is a small telescope with few elements: one plus lens as the eyepiece, a mirror to reflect the image, a prism in the middle to invert the image, and a plus lens as the objective. There are many equations that will describe the image size, the distance, and the magnification of such systems; however, I choose not to invoke the mathematical monstrosity with a lecture. Instead, I simply give a telescope to each group and ask them to take apart the telescope, list the elements, look at various objects through each, put them back together, and answer just one question: “What happens to the light rays that enter the system at each element?”

Right away the students are off to start writing and making sketches. At this point I just need to go around and answer any questions they have. Once I start hearing “oohs” and “ahas,” I know the students are starting to understand the physical effects of each of the telescope elements. The math comes naturally once the students understand what physically happens to the light rays that are squeezed, expanded, reflected, and bent. A colorful short clarifying sketch on the whiteboard easily sums up the discussion section, explaining how the projected image relates to the real-world object. Their field of view has just expanded.

One very revealing indication of the success of my teaching effort is that nearly all sixty students attend my discussion section every time. They all love the simple demonstrations that I frequently bring to the section. Many students have come up to me after class telling me how much more they understand through such demonstrations. The demonstrations also greatly encourage class participation by allowing students to interact with one another, debating what occurs with each element and fully understanding the combined result. In the end, the students have not only passed the class, they have gained a deeper appreciation for the optics of the eye.